In short: The most accurate way to measure ring size at home is a set of graduated ring gauges, tried on at the end of the day and choosing one that slides on easily but needs a gentle pull over the knuckle. If you already have a ring that fits, a marked ring stick is the most reliable remote method; string and ruler is only a rough guide.
A ring is the one piece of jewellery where being half a size out is the difference between "perfect" and "unwearable" — and unlike a bracelet, you can't just ease it on. Whether you're sizing your own finger or a customer's, getting an accurate measurement before you cut any metal saves a remake. The good news: there are three reliable ways to do it at home, and they take minutes.
Method 1: a ring gauge set (the professional way)
The most accurate method is a set of graduated ring gauges — a fan of rings in every size that you try on directly. A metal ring-sizer gauge set covers UK A–Z plus US, EU and international scales, so you read the size straight off the band that fits. Try them on at the end of the day, when fingers are at their largest, and aim for a gauge that slides on easily but needs a gentle pull over the knuckle.
Method 2: a ring stick (for an existing ring)
If you already have a ring that fits the right finger, slide it onto a marked ring stick and read where it sits. A marked ring stick gauge does this in seconds, and a steel ring sizer mandrel doubles as a forming tool when you come to make the ring. This is the most reliable remote method — far better than guessing from a string.
Method 3: the string-and-ruler method (and why to be careful)
No tools to hand? Wrap a thin strip of paper or string around the base of the finger, mark where it overlaps, and measure the length in millimetres — that's the inside circumference. Convert with a chart (UK size N ≈ 53.8 mm, for example). But measure the circumference, never the diameter, and don't pull the string tight; this method is the least accurate and is best treated as a rough guide to confirm with a gauge.
The mistakes that cause wrong sizes
Cold fingers (measure warm), measuring over a knuckle that's much larger than the base, sizing a wide band the same as a thin one (wide bands need a half-size up), and trusting a single reading. Measure twice, and for a band over about 6 mm wide, go up a touch. For the tools themselves, browse Measuring & Marking and Mandrels & Sizing.
Once you have the size, the making begins. Our guides to choosing a ring mandrel, sizing and stretching a ring, and measuring accurately at the bench take it from a number to a finished band.
Find ring gauges and sticks in Measuring & Marking and Mandrels & Sizing.
Frequently asked
How do I measure my ring size with string or paper?
Wrap a thin strip of paper or string around the base of the finger, mark where it overlaps and measure the length in millimetres: that is the inside circumference. Convert it with a chart, for example UK size N is about 53.8 mm. Measure the circumference, never the diameter, don't pull tight, and confirm the result with a gauge.
Do wide ring bands need a bigger size?
Yes. A wide band should not be sized the same as a thin one, because wide bands need a half-size up. For a band over about 6 mm wide, go up a touch from the size you measured, and measure twice before committing.
Why does my ring size measurement keep coming out wrong?
Cold fingers, measuring over a knuckle that is much larger than the base of the finger, and trusting a single reading are the usual causes. Measure when your fingers are warm, and measure twice before cutting any metal, because being half a size out is the difference between perfect and unwearable.